1. Field of the Invention
The present invention relates to an amorphous magnetic material suitable for a saturable magnetic core used as a saturable reactor or a noise suppressor, or a magnetic core used for an accelerator or a laser power supply, and a magnetic core using thereof.
2. Description of the Related Art
Switching power supplies are used in abundance as stabilizing power supplies of electronic instruments. In particular, a switching power supply assembled a magnetic amplifier (refers to as "magamp" hereinafter) for output control is being widely used due to its easiness in obtaining multiple outputs and its low noise.
A magamp is mainly composed of a saturable reactor, as a main portion thereof a saturable core is used. In a switching power supply, a saturable core is used also as a noise suppressor. For a constituent material of such a saturable core, since excellent square magnetization property is required, mainly, an Fe-Ni based crystalline alloy (permalloy) or a Co based amorphous magnetic alloy have been used.
However, in accordance with a recent demand for miniaturization, light weight, high performance of electronic instruments, a switching power supply is also strongly demanded to be miniature, light weight. Therefore, in a switching power supply, a switching frequency tends to be made higher. However, an Fe-Ni based crystalline alloy being used conventionally has such a defect that its coercive force becomes large in higher frequency region, resulting in remarkable increases of an eddy current loss. Therefore, it is not suitable for application in the high frequency region.
Besides, a Co based amorphous magnetic alloy, in addition to its excellent squareness characteristics and thermal stability, has an excellent property such as small loss even in the high frequency region. However, because of much inclusion of expensive Co, it has a difficulty that a manufacturing cost of a saturable core becomes high.
As amorphous magnetic materials other than Co based one, an Fe based amorphous magnetic alloy is being used in various fields, in addition, a micro-crystalline Fe based soft magnetic alloy is also known. However, these magnetic materials are large in their coercive force and maximum magnetic flux density B.sub.m, resulting in a large loss in a high frequency region. Therefore, they are not suitable for a saturable core material.
Increase of the loss in a high frequency region also becomes a problem when an Fe based amorphous magnetic alloy is employed for a magnetic core other than a saturable core. Though an Fe based amorphous magnetic alloy has been used as a constituent material of such as a choke coil or a transformer, a higher frequency tendency invites a problem of the increase of the loss. The Fe based amorphous magnetic alloy also has a defect of being low in its thermal stability of the magnetic properties.
Further, both the conventional Co based amorphous magnetic alloy and Fe based amorphous magnetic alloy are high in their melting points, as a result, when thin film is formed with such as a liquid metal quenching method, tends to become rough in their surface roughness. Lowering of surface property of an amorphous magnetic alloy thin ribbon, when being wound or laminated to form a magnetic core, becomes a cause of deterioration of magnetic property such as squareness ratio.
As a conventional amorphous magnetic material, other than the Co based or Fe based amorphous magnetic alloy, an amorphous magnetic alloy based on Fe-Ni is known. For instance, Japanese Patent Application Laid-Open No. Sho-58(1983)-193344 discloses an amorphous magnetic alloy possessing a composition expressed by (Fe.sub.1-a Ni.sub.a).sub.100-x-y Si.sub.x B.sub.y (0.2.ltoreq.a.ltoreq.0.4, 20.ltoreq.x+y.ltoreq.25 at %, 5.ltoreq.x.ltoreq.20 at %, 5.ltoreq.y .ltoreq.20 at %).
Further, Japanese Patent Application Laid-Open (Kohyo) No. Hei-4(1992)-500985 discloses a magnetic metallic glass alloy which has a composition expressed by Fe.sub.a Ni.sub.b M.sub.c B.sub.d Si.sub.e C.sub.f (here, M is Mo, Cr, 39.ltoreq.a.ltoreq.41 at %, 37.ltoreq.b.ltoreq.41 at %, 0.ltoreq.c.ltoreq.3 at %, 17.ltoreq.d.ltoreq.19 at %, 0.ltoreq.e.ltoreq.2 at %, 0.ltoreq.f.ltoreq.2 at %) and at least 70% thereof is glassy. Japanese Patent Application Laid-Open No. Hei-5(1993)-311321 discloses a super-thin soft magnetic alloy ribbon possessing a composition expressed by Fe.sub.100-x-y-z Ni.sub.x Si.sub.y B.sub.z (1.ltoreq.X.ltoreq.30 at %, 10.ltoreq.Y.ltoreq.18 at %, 7.ltoreq.Z.ltoreq.17 at %, X+Y+Z&lt;80 at %).
The above described respective amorphous magnetic alloy, though Fe-Ni is a base component of a magnetic alloy, is an Fe rich magnetic alloy of which main component is Fe. Therefore, as identical as the above described Fe based amorphous magnetic alloy, it has a defect of the loss being large, further, thermal stability of magnetic properties being low. When a thin film ribbon is formed with a liquid quenching method or the like, that similarly tends to cause a defect of being large in its surface roughness.
In addition, Japanese Patent Application No. Sho-60(1985)-16512 discloses an amorphous magnetic alloy which has a composition expressed by (Fe.sub.1-a Ni.sub.a).sub.100-y X.sub.y (X is Si and B, 0.3.ltoreq.a.ltoreq.0.65, 15&lt;y.ltoreq.30 at %) and is excellent in its corrosion resistivity and in its stress-corrosion cracking resistance. Japanese Patent Application Laid-Open No. Sho-57(1982)-13146 discloses an amorphous alloy expressed by (Fe.sub.1-a Ni.sub.a).sub.100-x-y Si.sub.x B.sub.y (0.2.ltoreq.a.ltoreq.0.7, 1.ltoreq.x.ltoreq.20 at %, 5.ltoreq.y.ltoreq.9.5 at %, 15.ltoreq.x+y.ltoreq.30 at %).
These amorphous magnetic alloys, as identical as the above described Fe-Ni based amorphous magnetic alloys, have basically Fe rich alloy compositions. Further, since they are not expected to be used as constituent material of such as a saturable core, a low-loss core, a high permeability core, the composition ratio of Si or B does not correspond to usage in a high frequency region, further, additive elements other than these primary components also are not fully investigated.
As described above, a Co based amorphous magnetic alloy conventionally used as a saturable core material, because of high content of the expensive Co, has a defect that the manufacturing cost of a magnetic core is high. Besides, among magnetic materials other than Co based one, an Fe based amorphous magnetic alloy and an Fe rich Fe-Ni based amorphous magnetic alloy have defects such that they are large in their loss in a high frequency region and low in their thermal stability. Further, anyone of the conventional amorphous magnetic alloys has a high melting point, and, as a result, when a thin film ribbon is formed with a liquid quenching method, its surface roughness tends to become large.